Ritualized Magic in your Fate game

Although Dresden Files is in playtesting as we speak, my group is about to start a homebrew urban fantasy game and that means magic rules. Here are the rules I've whipped up for magical rituals. Magic on the fly is based an entirely different subsystem that I might share if there's interest. As with all my homebrews, this is not neccesarily original, and has been heavily influenced by my lurking on the FATErpg group.

A magic ritual can be extremely powerful because of the many options spellcasters have available to them. By manipulating the materials, environment, and length of the ritual, ritualists can rack up large bonuses. Ritual magic is also particularly powerful thanks to its improvisational nature; almost any effect is possible.

Step One: Negotiate Effect with the GM
The intent of the spell should be clear before any dice are rolled. Almost any effect is potentially possible, but some might be considered too difficult to even attempt. For instance, mind control might not be available in the setting your group is using.

Most spells will either attempt to place aspects on a target or duplicate the effect of a mundane skill --possibly on a larger scale. Many rituals, especially wards and protection spells, may also be modeled by blocks.

Step Two: Gather Mystical Energy
A Gather roll is a Ritualism roll made to summon or collect the energy for a spell. A Gather roll may be subject to a penalty or bonus based on the caster's tradition. Situational aspects like "Mars in the Fifth House," "Ley-Line Nexus," or "The Power of Stone Henge" can be tagged to gain a bonus to the Gather roll.

Step Three: Focus Mystical Energy
A Focus roll is a Ritualism roll made to channel or direct the energy gathered into the desired effect. A Focus roll may be subject to a penalty or bonus based on the caster's tradition. Situational or item aspects like "Summoner's Crystal" or "Rosecrutian Pentacle" may be tagged for a bonus on the Focus roll.

Step Four: Determine Effect and Backlash
The result of the Gather roll is used to determine effect. (For instance, a Superb Gather roll is considered Superb for comparison to difficulty.) The result of the Focus roll is used to determine if the ritual will cause a backlash consequence. If the Focus roll is equal to or greater than the Gather roll, then the ritual will not result in a Backlash consequence. A Gather roll that is greater than the Focus roll will result in backlash. See the GM section for more information.

Step Five: Tweak the Result
It is possible to manipulate shifts to generate a result that is more desirable to the caster. Any penalties can be reduced by spending Focus shifts. For instance, each -1 penalty assigned by the GM for range or complexity can be ignored by spending one shift. Casters may, if they wish, spend shifts of Focus until the Gather roll is one point higher than the Focus roll. Shifts may also be gained or spent by moving the casting time up or down on the time increment chart. Rituals are assumed to take "a few hours" by default.

Instant
A few moments
Half a minute
A minute
A few minutes
15 minutes
Half an hour
A few hours
An afternoon
A day
A few days
A week
A few weeks
A month
A few months
A season
Half a year
A year
A few years
A decade
A lifetime

Example:
Jessica is performing a Thaumaturgey ritual that will destroy a nearby derelict building. Her GM assigns a -3 penalty for the range of the ritual. Jessica rolls Gather and achieves a Superb result. Her GM informs her that this would be good enough to sufficiently damage the building except for the range penalty.

With this in mind, Jessica rolls her Focus roll and gets a Superb result. This is enough to prevent backlash, but not good enough to provide shifts. She tags the situational aspect "Pentacle of Power" to get a +2 bonus to the Focus roll, and spends these shifts to ignore 2 points of the penalty. She also extends the ritual's casting time from "a few hours" to "an afternoon" and spends the resulting shift to ignore the leftover -1.

This gives Jessica a Superb result and no Backlash consequence.

Notes for the GM
The trickiest part of this magic framework is setting difficulties. For many spells, difficulty can be based of the difficulty that would be used for a mundane skill check. If a ritualist wants to use a spell to repair an old, rusted-out car, use the same difficult you would use if a mechanic attempted the same task using their Engineering skill. However, you may want to increase the difficulty if the task would require tools or materials or if it would normally take longer than the default ritual length (A few hours.)

Backlash consequences are meant to model the "risk" of backfiring magic in a fun, story-based way. Backlash consequences are minor by default, but a spellcaster may have to "roll-up" to a more severe consequence. Stress boxes can never prevent a Backlash consequence.

Allow your players to pick their own consequences with guidance from you. Consider the ritualist's magical tradition when picking consequences. For instance, a demon summoner might find herself plagued by an "Imp on the Loose!" or an Alchemist might find himself turned into a "Toad." Remember that these consequences can be compelled or invoked like any other aspect.

Most ritualists will follow a particular magical tradition. You may wish to prepare these before play, or you might like to let players make up their own. Most traditions will have a +1 to either the Gather roll or the Focus roll and a -1 to the other. Traditions should also receive a +1 to both rolls in some narrow circumstance. For instance, Thaumaturge's might get a +1 when creating magical wards.